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We report on a search for the non-standard-model process u(c)+g→t using pp̄ collision data collected by the Collider Detector at Fermilab II detector corresponding to 2.2fb-1. The candidate events are classified as signal-like or backgroundlike by an artificial neural network. The observed discriminant distribution yields no evidence for flavor-changing neutral current top-quark production, resulting in an upper limit on the production cross section σ(u(c)+g→t)<1.8pb at the 95% C.L. Using theoretical predictions we convert the cross section limit to upper limits on flavor-changing neutral current branching ratios: B(t→u+g)<3.9×10- 4 and B(t→c+g)<5.7×10-3. © 2009 The American Physical Society.

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Physical Review Letters